Towbar wiring for a W212 E350 estate 2011

[BelfastBill]

Hi I'm going to fit a towbar to my wife's E350 and was wondering the easiest way to wire it up, I'm on after one plug for a camping trailer so any help would be appreciated. Also I haven't bought a kit yet so any advice would be more than welcome. I don't want to have to bother with coding if I can get away without it.
Thanks Bill.
PS anyone on here have a cheap kit please?
Sorry I haven't been on here in a while but I've been in poor health for a while.

 

[ALFAitalia]

I think you will have to code it.....its connecting into the canbus system....so the ECU will need to know about the changes. One plug you say?....so 7 pin or 13 pin. The local towbar guy I use for work told me that some of the bespoke plug and play wiring looms (that plug straight into the car with no cutting of wires) cost nearly as much as the actual tow bars these days!!!

 

[BelfastBill]

Just looking at a 7 pin, saw some on Ebay that run from the battery and don't affect the canbus ,don't know if anyone here has any experience with those, some being sold by towtrusr.
Thanks for your help.

 

[ALFAitalia]

But they need to be connected into the lighting side of the canbus...

 

[BelfastBill]

Thanks just looked at the kit and it by passes the canbus, do you know if you have to remove the bumper or can they be fitted with the bumper in situ? If the bumper needs removing is it a difficult job.

 

[ALFAitalia]

How does it connect to the lighting system then? Cus cutting into the wiring or scotchlocks etc is a no no on a canbus car.

 

[fifermerc]

Thanks just looked at the kit and it by passes the canbus, do you know if you have to remove the bumper or can they be fitted with the bumper in situ? If the bumper needs removing is it a difficult job.

You will have to remove the bumper, as the tow bar replaces the crash bar mounted behind the bumper. I also doubt whether you can just chop into your lighting cables with scotchlocks.

 

[Trickythemerc]

If the vehicle has parking sensors it will need to have them disabled when towing a trailer. This needs to done via whatever the tow bar fitters use.

 

[BelfastBill]

Can the parking sensor not be turned off at the dash? Or remove the fuse when towing ?Thanks for all the help.

 

[BelfastBill]

Bump please

 

[Chalky600]

Hey Bill

did you get an answer to the wiring setup?

I have to do the same thing and have a universal bypass relay which came supplied with the tow bar.. instructions are minimal

Thanks

 

[Justintyme]

I've done it in my 2014 Eclass w212 using a "smart" relay, and blue block connectors to link the light cables to the relay, and from the relay to the towbar socket. I used the 12.v socket in the boot for the power supply. The only problem that I met was that the park/brake light is combined with a single cable feed and when the brake is pressed, its sends a "stronger" signal ( or want of a better word) to the display, causing it to "brighten"., giving the "brake Light " effect. The way around that is to locate the 3rd brake light feed (the brake light in the rear window) and to take the feed from that to the relay. If you need, I can give you the wiring diagram for the rear lights, and you can trace the 3rd brake light from that. Its more than 3 years since I have done it, and its been working 100% since then. Because its only a 7 pin trailer wiring, It hasn't interfered with the canbus, or thrown any fault codes. For caravans etc. I'm not sure.

 

[Chalky600]

Thank you so much for the swift reply.

The relay Kit that came with the towbar says that it is smart, so fingers crossed

Mine also is only be a 7 pin connector, mainly for a bike rack.

Id appreciate the wiring diagram for the third brake light.

That piece of information alone has probably saved me hours of head scratching.

 

[Justintyme]

Hi Chalky, I've attached the rear section of a w212 MB sedan wiring diagram, showing the cable feeding the 3rd brakelight. Its marked CENTRE STOP LIGHT. It may differ from the estate version, but you can check it out. I have the diagram for the front section too if you need it, OK.?

 

[Chalky600]

Thanks again

I have no excuse now but to pull the bumper off and get on with it

 

[Justintyme]

Thanks again

I have no excuse now but to pull the bumper off and get on with it

Have fun!!!

 

[JcbPaul]

I've done it in my 2014 Eclass w212 using a "smart" relay, and blue block connectors to link the light cables to the relay, and from the relay to the towbar socket. I used the 12.v socket in the boot for the power supply. The only problem that I met was that the park/brake light is combined with a single cable feed and when the brake is pressed, its sends a "stronger" signal ( or want of a better word) to the display, causing it to "brighten"., giving the "brake Light " effect. The way around that is to locate the 3rd brake light feed (the brake light in the rear window) and to take the feed from that to the relay. If you need, I can give you the wiring diagram for the rear lights, and you can trace the 3rd brake light from that. Its more than 3 years since I have done it, and its been working 100% since then. Because its only a 7 pin trailer wiring, It hasn't interfered with the canbus, or thrown any fault codes. For caravans etc. I'm not sure.

Hi, i was just reading through this post and looking for some advice! I have just fitted a towbar to my 2012 E250 saloon but i don't have a 12v socket in the boot but it does have the auxiliary battery in the boot. So i am wondering where would be best to get the 12v feed from? I am using the witter universal bypass kit and will only be towing a small trailer occasionally. Any advice would be really appreciated. Thanks.

 

[Justintyme]

Hi, i was just reading through this post and looking for some advice! I have just fitted a towbar to my 2012 E250 saloon but i don't have a 12v socket in the boot but it does have the auxiliary battery in the boot. So i am wondering where would be best to get the 12v feed from? I am using the witter universal bypass kit and will only be towing a small trailer occasionally. Any advice would be really appreciated. Thanks.

Hi, No. I wouldn't advise it. If your nearest power supply is the cigar lighter on the console between the front seats, it's that or from the battery direct. Bear in mind that those cigar lighter sockets can be fused for pretty high amperage, so better use a smaller fused link on the cable, as near the socket as possible.
Its not such a big deal running a cable direct from the battery to the boot either, especially if you have access to a lift. Same conditions apply... fusible link, as close as possible to the terminal. I've done it several times, and is a bit awkward, but not too much either. Best of Luck with it, and you are lucky in that in the 2012 E class, the brake and park lights are standard bulbs, needing a separate feed, unlike the 2014 E class,,they have the new system, one micro cable supplying both brake and park lights

 

[Chalky600]

Hi, i was just reading through this post and looking for some advice! I have just fitted a towbar to my 2012 E250 saloon but i don't have a 12v socket in the boot but it does have the auxiliary battery in the boot. So i am wondering where would be best to get the 12v feed from? I am using the witter universal bypass kit and will only be towing a small trailer occasionally. Any advice would be really appreciated. Thanks.

I used the Aux Battery in the boot as a power supply on my E250 and it works fine. I also located the unit in the space next to the battery

The kit i had included a fuseable lead so all is good.

The kit i used also senses whether the tail / Brake lights are activated from a single cable so the wiring was pretty simple

 

[JcbPaul]

Hi, No. I wouldn't advise it. If your nearest power supply is the cigar lighter on the console between the front seats, it's that or from the battery direct. Bear in mind that those cigar lighter sockets can be fused for pretty high amperage, so better use a smaller fused link on the cable, as near the socket as possible.
Its not such a big deal running a cable direct from the battery to the boot either, especially if you have access to a lift. Same conditions apply... fusible link, as close as possible to the terminal. I've done it several times, and is a bit awkward, but not too much either. Best of Luck with it, and you are lucky in that in the 2012 E class, the brake and park lights are standard bulbs, needing a separate feed, unlike the 2014 E class,,they have the new system, one micro cable supplying both brake and park lights

That's great! Thanks for all the info really appreciated. Hopefully i will get it done this evening.